Hi,
Just looking at this thread (and loads of others), but still having issues.
I'm using Windows 10 build 1607 (install media and WinPE)
I am configuring iPXE and Tiny PXE ok
I successfully connect to a Starwind iSCSI target.
I can do a Windows 10 install, which fails right at the end with an error regarding missing required driver (this is on a Hyper-V gen 1 guest and a physical box)
I have also installed to a local drive then used Clonedisk to copy an install to an iSCSI drive mounted in WinPE via iSCSI Initiator
I've managed to edit BCD to ensure that there is everything on the single "C" partition (also made sure it is active in diskpart).
However when it boots i get the Windows starting logo, but as soon as i get the spinning dots i see the iSCSI connection drop in Starwind.

I can confirm i DO have the keep-san setting in iPXE (even running sanboot --keep when i've successfully sanhooked the drive to make sure)

I just wanted to detail the some steps I took to getting Windows 10 to directly install directly to a FreeBSD iSCSI target.

We have a few Supermicro boxes with Intel x520-DA2 NICs which were booting fine Windows 7 from a FreeBSD target.

We initially tried installing Windows 10 (1709 build) directly to these targets on the machines and got the dreaded drivers not signed error on first boot. Setting allow unsigned continued this boot, but the second boot would go into recovery. This was using undionly.kpxe. This was using the latest version of iPXE in the repo as of today.

Based on the forum advice we switched to ipxe.pxe, however the Windows installation would state this is not a bootable device (and diskpart would report the same) and it could not install.

We then switched over to the newer 1804 build using ipxe.pxe, however the Windows installer would state the same thing (could not install to non bootable device). Switching it back to undionly.kpxe allowed the install to continue. We also updated the Intel drivers to the latest at this point as a matter of course, even though the drive showed up here just like the 1709 build (however we never tested the 1804 build without doing this).

The machine now boots fine to the desktop after multiple restarts and it's running like a champ.

So if you are having troubles, try out the latest 1804 build, upgrade the drivers even if the drive already shows up and switch between undionly/ipxe.pxe (the advice here states only ipxe.pxe works, but this seems hardware dependent).